Impact-absorber devices, impact-absorption method, and framework and vehicle including such impact-absorber devices

ABSTRACT

The invention concerns impact-absorber devices, an impact-absorption method, and a framework and a vehicle including such impact-absorber devices. According to the invention, the impact-absorber device comprises at least one longitudinal member absorbing by deformation the energy generated by an impact in a given direction, which member is made from thin plate, having a generally triangular cross-section in a plane perpendicular to the direction of impact. Applications to rail vehicles, for example.

The invention concerns impact-absorber devices, an impact-absorptionmethod, and a framework and a vehicle including such impact-absorberdevices. The instant application contains subject matter related to thatof copending application Ser. No. 08/227,010, which was filed on Apr.13, 1994, now U.S. Pat. No. 5,462,144 and is assigned to the sameassignee.

BACKGROUND OF THE INVENTION

Some prior art impact-absorber devices are in the form of reversibledeformation systems based on dissipation of energy by dry or viscousfriction. In rail transport applications they are incorporated in thebuffers and in the bodies of automatic couplings. These systems have thedrawback of a low unit energy absorption capability, around 50 kJ perunit.

Another impact-absorber device is the shield disposed on the motivepower unit of a train, especially high-speed trains. The shield has ahoneycomb or tube construction deforming in compression. It is a largemember attached to the train and has the drawback that it does notcontribute to the transmission of longitudinal forces in the chassis.Also, it protects only the driver.

The safety of train passengers in the event of a collision is currentlya matter of great concern. Increasing train speeds increase the dangerin the event of an accident. A recent spate of accidents has shown thatimprovements in signalling have not eliminated all risks of collision.

An impact-absorber device that is more effective than current devices istherefore required. This device must, on impact, bring about lengthwisecollapse of the axis of the motive power unit to prevent the latterfront skewing on the track. It must also be light enough to satisfytrain axle load limits. It must also be compact in size, since spacesaving is most important in the motive power units and in the passengercars.

OBJECTS AND SUMMARY OF THE INVENTION

The present invention mitigates the drawbacks of the prior art and meetsthe stated requirements in terms of effectiveness, weight and overallsize. It finds a particularly beneficial application in rail transportwhere the amount of energy to be absorbed on impact can be considerable.It can nevertheless be used in other fields to absorb impact between amoving vehicle and an obstacle or between two moving vehicles (cars,lifts, etc).

The effectiveness of the proposed device resides in the specific shapeof its section transverse to the direction of impact.

The invention consists in an impact-absorber device comprising at leastone longitudinal member absorbing by deformation the energy generated byan impact in a given direction wherein said member is made from thinplate, having a generally triangular cross-section in a planeperpendicular to the direction of impact.

Said member can have two parallel opposite sides and two sides formingwith one of the parallel sides a longitudinal member having a generallytriangular transverse cross-section.

The invention also consists in a framework including at least oneimpact-absorber device disposed between non-deformable parts of theframework.

The invention further consists in a vehicle including a frameworkaccording to the invention.

The invention further consists in an impact-absorption method wherein,in the event of a frontal impact, the passenger and driver areas of thevehicle do not undergo any plastic deformation before all possibleenergy has been absorbed by the impact-absorber devices.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the invention emerge from thedescription of the impact-absorber device and impact-absorption methodof the invention given with reference to the accompanying drawings, inwhich:

FIG. 1 shows an impact-absorber device of the invention constituted by asingle longitudinal member,

FIG. 2 shows a different embodiment of the impact-absorber device of theinvention,

FIG. 3 shows a further embodiment of the impact-absorber device of theinvention,

FIG. 4 shows a rail vehicle chassis incorporating impact-absorberdevices of the invention,

FIG. 5 shows part of the rail vehicle chassis from FIG. 4 incross-section on the line V--V,

FIG. 6 shows part of the rail vehicle chassis from FIG. 4 incross-section on the line VI--VI,

FIG. 7 shows the rail vehicle chassis from FIG. 4 in cross-section onthe line VII--VII,

FIG. 8 shows a rail vehicle body framework incorporating impact-absorberdevices of the invention,

FIG. 9 shows part of the rail vehicle body framework from FIG. 8 incross-section on the line IX--IX,

FIG. 10 shows part of the rail vehicle body framework from FIG. 8 incross-section on the line X--X,

FIG. 11 shows the rail vehicle body framework from FIG. 8 incross-section,

FIGS. 12a through 12d and 13a and 13b respectively show various stagesin the collapse of the third and fourth impact-absorber devices,

FIGS. 14a and 14b through 17a and 17b show four stages in thedeformation of the framework of the rail vehicle body incorporating theimpact-absorber devices of the invention.

MORE DETAILED DESCRIPTION

The impact-absorber device shown in FIG. 1 comprises a singlelongitudinal member 1 aligned with the impact direction Oz. Thecross-section of this member is in the xOy plane perpendicular to theimpact direction and it is in the shape of two triangles 2 and 3 havinga common vertex. The sides of the triangles 2 and 3 are the metal wallsof the member 1. The sides of the triangles can be straight or slightlycurved. The vertices of the triangles can optionally be rounded, asshown in the figure.

The member 1 is made from thin plate. In the case of FIG. 1 it isconstructed from three plates 4, 5 and 6 welded together by weld beads7, 8, 9 and 10. The plates 4 and 6 are bent to form two corners of thetriangles 2 and 3.

The material from which the thin plates is made depends on the amount ofenergy that the device is intended to absorb. Steel allows a largeamount of energy to be absorbed.

The member 1 is made from thin plate so that in the event of an impactof sufficient energy it collapses concertina fashion in the direction ofimpact. Impact tests have shown that this structure behaves in a doublyadvantageous manner. Firstly, it can collapse by about 70% of itsoriginal length, which is exceptional. Secondly, it collapses withoutany generalized buckling of the member, which collapses without anychange in its direction.

The thickness of the thin plate depends on the outside dimensions of themember. The member must be able to collapse concertina fashion on impactdue to localized buckling of the thin plates. Calculation andexperiments can optimize the thickness as a function of the outsidedimensions of the member for a given amount of energy to be absorbed.

For reasons of symmetry the best results are obtained for across-section of the member including two identical triangles facing inopposite directions. In other words, the cross-section is X-shaped, withtwo opposite sides closed.

In use, or for the purposes of an impact test, the ends 12 and 13 arewelded to respective brackets, the member having to absorb the energyassociated with an impact by virtue of its deformation. The membercollapses concertina fashion substantially within its original outline.

Localized strengthening members 11 can be provided between the twotriangles 2 and 3 in planes perpendicular to the impact direction. Theyare advantageously attached by welding and improve the torsionalstability of the member 1.

In the embodiment shown in FIG. 2 the plates 4, 5 and 6 are stamped inlocalized areas like the areas 14. The shape and location of the stampedareas can be determined by calculation and experiment.

The device 15 shown in FIG. 3 can absorb impacts of greater energy thanthe device described above. The basic structure is the same as that ofFIG. 1 and the same component parts are identified by the same referencenumbers. The corners between the triangles 2 and 3 are now closed bythin plates 16 and 17 welded by respective weld beads 18, 19 and 20, 21to the remainder of the member.

If collapse along the Oz axis occurs as previously described the plates16 and 17 become corrugated, the outline of the member remainingapproximately the same.

An impact-absorber device can combine a plurality of members like themembers 1 and 15 in parallel to absorb impact over a relatively largearea. A device of this kind can be used on rail vehicles to absorbviolent impact occurring in the event of an accident. In this case it isparticularly advantageous to integrate the device into a rail vehiclechassis to constitute a "fuse" area to protect against the consequencesof an accident.

FIG. 4 shows a rail vehicle chassis 25 including two impact-absorberdevices 26 and 27 in accordance with the invention. The chassiscomprises two side sills 31 and 32 between which are two pivot beamsadapted to rest on bogies: the front pivot beam 33 and the rear pivotbeam 34. At the rear, the side sills 31 and 32 are joined by a rearcrossbeam 35. At the front the side sills 31 and 32 and the front pivotbeam 33 are extended by a front part including the impact-absorberdevice 27.

Sole bars 36 and 37 interconnect the pivot beams 33 and 34. They areaccompanied by other sole bars: the sole bars 40 and 41 extendingforwardly from the pivot beam 33.

At the rear of the chassis 25 the impact-absorber device 26 is disposedbetween the rear crossbeam 35 and the ends of the side sills 31, 32 andthe pivot beam 34. The device 26 includes a plurality of members. Themembers 42 and 43 on the outside are inserted into the side sills 31 and32. The members 44 and 45 on the inside extend the members 38 and 39 asfar as the rear crossbeam 35.

For the energy absorbing members to collapse effectively in the event ofa violent impact the other component parts of the chassis must be muchless deformable than the members 42, 43, 44 and 45. Localizedstrengthening of the chassis framework can achieve this.

As the space around a pivot beam is usually congested, the length of thedevice 26 has deliberately been kept small. The members 42 and 43 arelonger than the members 44 and 45 (see FIG. 4).

The members 44 and 45 are welded to the rear crossbeam 35 via reinforcedportions 46 and 47 which widen in the direction towards the rearcrossbeam 35. The portions 46 and 47 provide bases for the members 44and 45. The member 44 is welded to the member 38 with a metal platebetween them providing a base for the member 44. The same applies to thejoining of the members 45 and 39. An intermediate crossbeam 48 is weldedbetween the members 38 and 39 near the members 44 and 45.

The members 42 and 43 are welded to the side sills 31 and 32 with metalplates providing bases for these members between them. The side sillsare strengthened where they are joined to the members 42 and 43 bystrengthening parts 49. These strengthening parts and the proximity ofthe pivot beam 34 and the rear crossbeam 35 stiffen the side sills sothat these portions of the latter can be regarded as undeformablecompared to the impact-absorber device.

FIG. 5 shows only the lefthand part of the cross-section plane V--Vshown in FIG. 4, the righthand part being a mirror image of the lefthandpart. The axis 51 is the central vertical axis of the vehicle. Themembers 42 and 44 are seen in cross-section. The member 42 is of thetype shown in FIG. 1. It is made up of a plurality of thin plates 52, 53and 54 bent as necessary and welded together. For joining on the sideplates it is necessary to add an appendix 56 in the lower portion weldedto the extension 55 of the plate 52. This has no unwanted repercussionson the system.

The member 44 is of the type shown in FIG. 3. It is made up of aplurality of thin plates 61, 62, 63, 64 and 65 bent as necessary andwelded together. The member 44 therefore has the same outside shape asthe sole bars of the chassis.

The stress concentrations in the cross-sections of the members 42 and 44are non-uniform and it is possible to compensate for the differentstresses by using different grades of the materials. With the chassismade from high yield stress steel (E490D grade), for example, the plates52, 53, 61, 62 and 65 can be made from E24 grade steel, the plates 63and 64 from E36 grade steel and the plates 55 and 56 from E490D gradesteel.

The plates can be 4 mm thick for a height h of 195 mm and a width l of110 mm for the member 42 and for a height h' of 130 mm and a width l' of220 mm for the member 44.

FIG. 6 shows only the lefthand part of the cross-section plane VI--VIshown in FIG. 4, the righthand part being a mirror image of the lefthandpart. The axis 171 is the central vertical axis of the vehicle. The sidesill 31 and the member 38 are seen in cross-section. The side sill 31 ismade from bent plate 71.

The member 38 is made by welding together plates 69, 70, 72, 73 and 74.

At the front of the chassis (see FIG. 4) the impact-absorber device 27comprises a central member 75 disposed along the central longitudinalaxis of the vehicle and two side members 76 and 77 arranged in aforward-pointing V-shape. This device is between a front end plate 78adapted to take any impact and a crossbeam 79 joined to the remainder ofthe chassis by a rigid mechanical structure transmitting forces betweenthe crossbeam 79 and the front pivot beam 33. This rigid structurecomprises the sole bars 40 and 41, the crossbeams 80, 81 and 82 and thegirders 83, 84, 85, 86, 87 and 88.

FIG. 7 shows the members 75, 76 and 77 in cross-section. The member 75is of the type shown in FIG. 3. It is formed from a plurality of thinplates 189, 190, 191, 192, 193, 67 and 68 welded together.

The members 76 and 77 do not have the X-shape structure which ischaracteristic of the invention. The member 76 is made up of a pluralityof thin plates 194, 195, and 196 bent as necessary and welded together.The plate 194 forms a diagonal of the rectangle of the cross-section ofthe member 76. This diagonal runs from the top lefthand corner to thebottom righthand corner.

The member 77 is made up of a plurality of thin plates 197, 198, 199bent as necessary and welded together. The plate 197 forms a diagonal ofthe rectangle of the cross-section of the member 77. This diagonal runsfrom the top righthand corner to the bottom lefthand corner.

Making the impact-absorber device by forming and drawing is also withinthe scope of the present invention.

FIG. 8 shows a front framework of a rail vehicle body including first,second, third and fourth impact-absorber devices 97, 98, 103 and 104 asdescribed above.

The front framework of the rail vehicle body comprises a chassis 25 madeup of two side sills 31 and 32 between which is disposed a front pivotbeam 33 resting on a front bogie.

First and second rigid rings 89 and 90 constitute a safety cage 91. Solebars 92 and 93 and reinforcing members 94 and 95 are fastened to therigid rings to stiffen the safety cage.

A first deformable area 96 constituting the front part of the frameworkis made up of first and second impact-absorber devices 97 and 98 and acoupling bar 122.

The first impact-absorber devices 97 are disposed on respective sides ofthe central axis of the chassis 25. These first impact-absorber devicesare generally trapezoidal and each is made up of a longitudinal member 1according to the invention to the top and bottom of which are fastenedtrapezoidal plates 99 and 100.

The second impact-absorber devices 98 are made up of a prior arthoneycomb type member. These second impact-absorber devices are disposedon the first impact-absorber devices 97, for example, the combinationbearing against a retaining plate 101.

The prior art coupling bar 122 is disposed longitudinally, preferablybetween the first impact-absorbing members 97 in the first deformablearea 96.

A second deformable area 102 is disposed between the first deformablearea 96 and the safety cage 91.

The second deformable area 102 is made up of third and fourthimpact-absorber devices 103 and 104 respectively in the lower and upperparts of this second deformable area.

The third impact-absorber devices 103 each comprise first and secondimpact-absorbing members 105 and 106 in accordance with the invention.The first and second impact-absorbing members 105 and 106 are disposedin a V-shape and triangular plates 107 and 108 are fastened to their topand bottom surfaces.

The plates 107 and 108 are preferably trapezoidal to absorb the initialforce of a frontal impact applied to the third impact-absorber devices103.

The third impact-absorber devices are disposed in the plane of thechassis 25 and bear against a crossbeam 109. The ends of the crossbeam109 are fastened to the base of the first rigid ring 89.

The fourth impact-absorber devices 104 each comprise first and secondimpact-absorbing members 110 and 111. The first and secondimpact-absorbing members 110 and 111 are disposed in a V-shape andplates 112 and 113 are fastened to their top and bottom surfaces.

The plates 112 and 113 are preferably trapezoidal to absorb the initialforce of a frontal impact applied to the fourth impact-absorber devices104.

The fourth impact-absorber devices are disposed in alignment with theupper part of the first rigid ring 89 and the second impact-absorbingmembers 98.

Depending on the shape of the ends of the upper part of the first rigidring 89 on which the impact-absorber devices 104 bear, the triangularplates 112 and 113 can constitute a single plane (FIGS. 13a and 13b) ortwo planes as shown in FIG. 8.

The other ends of the impact-absorber devices 104 bear on the holdingplate 101 through the intermediary of a support frame 118.

Guide means 119 fastened to the chassis 25 are disposed longitudinallyparallel to the longitudinal axis of the chassis 25.

FIG. 9 shows part of the rail vehicle body framework from FIG. 8 incross-section on the line IX--IX.

The members 105 and 106 and the trapezoidal plates 107 and 108 are seenin cross-section. The members 105 and 106 are of the type shown in FIGS.1 to 3 and as previously described.

The main effect of the trapezoidal plates 107, 108 is to tension thelongitudinal impact-absorbing members 105, 106.

As previously described the third impact-absorber devices 103 deformplastically concertina fashion in such a way that the outline of theimpact-absorber device is preserved.

FIG. 10 shows part of the rail vehicle body framework from FIG. 8 incross-section on the line X--X.

The members 110 and 111 and the trapezoidal plates 112 and 113 are seenin cross-section.

The first and second impact-absorbing members 110 and 111 each comprisea single longitudinal impact-absorbing member different from those shownin FIGS. 1 to 3. The cross-section of the longitudinal member isgenerally rectangular in shape with two parallel opposite sides 114 and115 and two other opposite sides 116 and 117 forming with one of theparallel sides a longitudinal impact-absorbing member with a generallytriangular transverse cross-section.

Because the first and second impact-absorbing members 110 and 111 arenot symmetrical the remarkable result of a frontal impact to these twomembers is a twisting effect rather than a buckling effect. As a resultof this, the fourth impact-absorber device 104 is deformed in a verticalplane that moves in the direction of the impact causing the deformation.This deformation in a vertical plane is related to the presence of thetrapezoidal plates 112 and 113.

As previously described, the fourth impact-absorber devices 104 deformplastically concertina fashion so that the external contour of theimpact-absorber device is preserved.

A vital consequence of the deformation in the vertical plane of thethird and fourth impact-absorber devices 103, 104 is that the supportframe 118 and the first rigid ring 89 remain parallel to each other inthe event of a frontal impact.

FIG. 11 is a cross-section view of the rail vehicle body framework fromFIG. 8.

FIG. 11 shows the chassis 25 comprising the two side sills 31 and 32between which is disposed the front pivot beam 33 resting on the frontbogie.

The first and second rigid rings 89, 90 constitute the safety cage 91.The sole bars 92 and 93 are fastened to the rigid rings.

The first deformable area 96, constituting the front part of theframework, comprises the first impact-absorbing members 97 and thesecond impact-absorbing members (not shown) and a coupling bar 122.

The first impact-absorber devices 97 are on respective sides of thecentral axis of the chassis 25. The first impact-absorber devices aregenerally trapezoidal and each comprises a longitudinal member 1 inaccordance with the invention.

The first impact-absorber devices 97 bear against the holding plate 101which is fastened to the support frame 118.

The second deformable area 102 is disposed between the first deformablearea 96 and the safety cage 91.

The second deformable area 102 comprises the third impact-absorberdevices 103 and the fourth impact-absorber devices (not shown).

The third impact-absorber devices 103 each comprise first and secondimpact-absorbing members 105, 106 in accordance with the invention thetop and bottom surfaces of which are fastened to trapezoidal plates 107and 108.

The third impact-absorber devices 103 are disposed in the plane of thechassis 25 and bear against a crossbeam 109. The ends of the crossbeam109 are fastened to the base of the first rigid ring 89.

The guide means 119 fastened to the chassis 25 are disposedlongitudinally parallel to the longitudinal axis of the chassis 25. Inthe preferred embodiment the guide means 119 comprise the longitudinalslider 120 adapted to slide in the longitudinal guide 121.

Also in the preferred embodiment the longitudinal guide 121 is fixed tothe chassis 25 and is delimited by the length of the safety cage 91.

The longitudinal slider 120 is fixed at one end, at the end adjoiningthe support frame 118, for example, in such a way that its other end canslide in the longitudinal guide 121.

The coupling bar 122 is disposed longitudinally, preferably between thefirst impact-absorbing members 97 in the first deformable area 96.

The coupling bar 122 bears against a first bearing plate 123 in such away that the bearing plate 123 and the end of the coupling bar 122 canslide in the longitudinal guide 121.

First, second and third longitudinal impact-absorbing members 124, 126and 128 in accordance with the invention are freely slidable in thelongitudinal slider 120.

These longitudinal impact-absorbing members in accordance with theinvention respectively constitute the fifth, sixth and seventhimpact-absorber devices.

The first and second longitudinal members 124, 126 bear against a secondbearing plate 125 in such a way that the second bearing plate 125 isable to slide in the longitudinal guide 121.

The second and third longitudinal members 126, 128 bear against thethird bearing plate 127 in such a way that the third bearing plate 127is able to slide in the longitudinal slider 120 and even in thelongitudinal guide 121.

The third longitudinal members 128 bear against a fourth bearing plate129 which is fastened to the pivot beam 33.

Table 1 summarizes the main technical data for each of theimpact-absorber devices used in the front framework of a rail vehiclebody in the preferred embodiment of the invention.

                                      TABLE 1                                     __________________________________________________________________________    ABSORBER                                                                              LONGIT                                                                              MATERIAL                                                                             WIDTH                                                                              HEIGHT                                                                              RATING                                        DEVICE  MEMBER                                                                              (STEEL)                                                                              mm   mm    kN                                            __________________________________________________________________________     97 (1st)                                                                              1    Z8 CN 12                                                                             250  150   1 000                                          98 (2nd)                                                                             prior art                                                             103 (3rd)                                                                             105   Z8 CN 12                                                                             100  150    400                                                  106                                                                   104 (4th)                                                                             110   Z8 CN 12                                                                             200  150    900                                                  111                                                                   124 (5th)                                                                             124   Z8 CN 12                                                                             250  170   1 100                                         126 (6th)                                                                             126   Z8 CN 12                                                                             250  170   1 400                                         128 (7th)                                                                             128   Z8 CN 12                                                                             250  250    1 700-                                                                       2 500                                         __________________________________________________________________________

In the event of a frontal impact, for example, between the vehiclefitted with impact-absorber devices of the invention and another vehicleor fixed buffers at the end of the track the impact-absorber devicescollapse.

By virtue of the basic technical effect of the invention the collapse ofthe impact-absorber devices results in concertina type deformation ofthe longitudinal impact-absorbing members. This deformation occurs in avertical plane which moves in the direction of impact.

As previously stated, the concertina type deformation of the membersoccurs in such a way that the external contour of the members isapproximately preserved.

FIGS. 12a to 12d and 13a and 13b show various stages in the collapse ofthe third and fourth impact-absorber devices 103, 104, respectively.

These figures show the concertina type deformation of theimpact-absorber devices and that their external contour is preserved.

The invention also concerns an impact-absorption method based on the useof the rail vehicle body framework incorporating impact-absorber devicesin accordance with the invention.

The impact-absorption method in accordance with the invention is suchthat in a frontal impact the passenger and driver areas do not undergoany plastic deformation before all possible energy has been absorbed bythe impact-absorber devices.

FIGS. 14a, 14b to 17a, 17b show four successive phases in thedeformation of the rail vehicle body framework incorporatingimpact-absorber devices of the invention.

In these figures the same reference numbers as used previously indicatethe same components.

FIGS. 14a, 14b to 17a, 17b show a coupling bar 130 disposed at the rearend of the rail vehicle body framework.

The coupling bar 130 includes a longitudinal impact-absorbing member 131of the invention and as shown in FIGS. 1 to 3 the outermost end of whichis adapted to slide in a longitudinal guide 132 fastened to the chassis25 of the framework.

The coupling bar 130 thus constitutes an eighth impact-absorber device.

Table 2 summarises the main technical data for the eighthimpact-absorber device used in the rear framework of the rail vehiclebody in accordance with the invention.

                                      TABLE 2                                     __________________________________________________________________________    ABSORBER                                                                              LONGIT                                                                              MATERIAL                                                                             WIDTH                                                                              HEIGHT                                                                              RATING                                        DEVICE  MEMBER                                                                              (STEEL)                                                                              mm   mm    kN                                            __________________________________________________________________________    130 (8th)                                                                             131   Z8 CN 12          1 100                                         __________________________________________________________________________

The first phase, shown in FIGS. 14a and 14b is suited to vehicle speedsin the range 0 m/s to 3 m/s. In this first phase the energy of theimpact is absorbed by elastic deformation of the coupling bar 122.

In this phase I, given the speed, the impact is "visco-elastic" and theacceleration does not exceed 3 g.

The coupling bar 122 undergoes longitudinal elastic displacement andenters the longitudinal slider 120 without any deformation of theframework, especially the impact-absorber devices.

The longitudinal displacement of the coupling bar 122 from its originalposition is in the order of 190 mm, for example. The original positionof the coupling bar 122 (before the impact) and its final position (atthe end of phase I) are shown in FIGS. 14a and 14b.

The second phase, shown in FIGS. 15a and 15b, is suited to vehiclespeeds between 3 m/s and 5 m/s.

The acceleration in this phase II does not exceed 5 g.

The coupling bar 122 is displaced longitudinally and enters further intothe longitudinal slider 120.

The energy is absorbed by plastic deformation of the fifth and eighthimpact-absorber devices 124, 130.

The longitudinal displacement of the coupling bar 122 relative to itsposition at the end of phase I is in the order of 550 mm, for example, adisplacement of 740 mm from its original position. The original positionof the coupling bar 122 and its final position (at the end of phase II)are shown in FIGS. 15a and 15b.

The third phase, shown in FIGS. 16a and 16b, is suited to vehicle speedsbetween 5 m/s and 10 m/s.

In this phase III the coupling bar 122 is displaced longitudinally andenters further into the longitudinal slider 120.

The energy is absorbed by plastic deformation of the first, second andsixth impact-absorber devices 97, 98 and 126.

The longitudinal displacement of the coupling bar 122 relative to itsposition at the end of phase II is in the order of 576 mm, for example,a displacement in the order of 1 286 mm from its original position. Theoriginal position of the coupling bar 122 and its final position (at theend of phase III) are shown in FIGS. 16a and 16b.

The fourth phase, shown in FIGS. 17a and 17b, is suited to vehiclespeeds in excess of 10 m/s.

In this phase IV the coupling bar 122 is displaced longitudinally andenters further into the longitudinal slider 120.

The energy is absorbed by plastic deformation of the third, fourth andseventh impact-absorber devices 103, 104 and 128.

The longitudinal displacement of the coupling bar 122 relative to itsposition at the end of phase III is in the order of 480 mm, for example,a displacement in the order of 1 766 mm from its original position. Theoriginal position of the coupling bar 122 and its final position (at theend of phase IV) are shown in FIGS. 17a and 17b.

We claim:
 1. A framework comprising:a longitudinal slider which is ableto slide without deformation within a longitudinal guide; and a firstimpact-absorber device located within, and able to slide relative to, atleast one of said longitudinal guide and said longitudinal slider, saidfirst impact absorber device plastically deforming by collapsingconcertina fashion in a direction of impact caused by an accidentalcollision.
 2. A framework according to claim 1 including anotherimpact-absorber device able to slide by collapsing concertina fashion insaid direction of impact in said longitudinal guide, one end of saidlongitudinal slider being able to slide without deformation in saidlongitudinal guide.
 3. A framework according to claim 2 including athird impact-absorber device fastened at one end to a chassis and withits other end adapted to slide in said longitudinal guide, saidlongitudinal guide being fastened to the chassis.
 4. A frameworkaccording to claim 2, including a third impact-absorber device fastenedto the end of a coupling bar and adapted to slide freely in saidlongitudinal slider.
 5. A framework according to claim 4 wherein thelongitudinal slider is fastened at one end to a support frame and atanother end is adapted to slide in said longitudinal guide, saidlongitudinal guide being fastened to a chassis.
 6. A framework,comprising:a first impact-absorber device, disposed betweennon-deformable parts of said framework, said first impact-absorberdevice comprising:a longitudinal member, absorbing by deformation impactenergy generated by an impact in a given direction; said member having afirst side parallel to a second side: said first side being connectedwith two other sides; said two other sides being inclined inwardly, andbeing connected to said second side; said member being made from thinplate; and said first side and said two other sides having a generallytriangular cross-section in a plane perpendicular to said givendirection; and a deformable area, including a second impact-absorberdevice in an upper part thereof, said second impact-absorber devicecomprising first and second impact-absorbing members, the top and bottomof which are fastened to trapezoidal plates.
 7. A framework,comprising:a first impact-absorber device, disposed betweennon-deformable parts of said framework, said first impact-absorberdevice comprising:a longitudinal member, absorbing by deformation impactenergy generated by an impact in a given direction; said member having afirst side parallel to a second side; said first side being connectedwith two other sides; said two other sides being inclined inwardly, andbeing connected to said second side; said member being made from thinplate; and said first side and said two other sides having a generallytriangular cross-section in a plane perpendicular to said givendirection; and a deformable area, including a second impact-absorberdevice in a lower part thereof, said second impact-absorber devicecomprising first and second impact-absorbing members, the top and bottomof which are fastened to triangular plates.
 8. An impact-absorber devicecomprising:an upper plate in vertical alignment with, and parallel to,an identical lower plate, said upper plate and said lower plateextending in a general direction of impact; and longitudinalimpact-absorbing members, including a first and a second member, inparallel with and connected between said upper and said lower plate, andextending in said direction of impact; wherein a respective centrallongitudinal axis of said first member is angled from the respectivecentral longitudinal axis of said second member; wherein each of saidmembers has a cross-section, in a plane perpendicular to said directionof impact, in the shape of two opposite triangles having parallel basesand a common vertex; and wherein each of said members is formed of metalplate, the thickness of which permits collapse, concertina fashion, insaid direction of impact; whereby said impact absorber device absorbs bydeformation impact energy generated by an impact in said givendirection.
 9. A safety cage for a vehicle, said safety cage comprising:aframework having a rigid ring, and a lower deformable area; said lowerdeformable area being disposed forward of said rigid ring along ageneral direction of impact; said lower deformable area having a lowerimpact-absorber device comprising: an first lower plate in verticalalignment with, and parallel to, an identical second lower plate, saidfirst lower plate and said second lower plate extending in said generaldirection of impact; and lower longitudinal impact-absorbing members,including a first and a second lower member, in parallel with andconnected between said first and said second lower plate, and extendingin said direction of impact; wherein a respective central longitudinalaxis of said first lower member is angled from the respective centrallongitudinal axis of said second lower member; wherein each of saidlower members has a cross-section, in a plane perpendicular to saiddirection of impact, in the shape of two opposite triangles havingparallel bases and a common vertex; and wherein each of said lowermembers is formed of metal plate; the thickness of which permitscollapse, concertina fashion, in said direction of impact; whereby saidlower impact absorber device absorbs by deformation impact energygenerated by an impact in said given direction.